82 



M. E. COLLETT 



creased. This is interesting, for, when the acid is omitted and 

 the salts are used alone, the addition of NaCl increases the toxicity 

 of CdCl2 and C0CI2 to Euplotes, just as it does with SrCl2. 



Turning, now, to the cyclic acids (tables 5, 9, 10), we find much 

 the same condition of affairs as with caproic, and like caproic 

 they are more difficult to antagonize than formic, acetic, or 

 butyric. These same lipoid-soluble acids were found by Harvey^ ^ 



TABLE 5 



BENZOIC 0.0005 N 



Concentration of salts M. 



Monovalent cations 



Bivalent cations 



Alone .... 

 Plus NaCl 

 Plus KCl . 



Plus BaCl2 

 Plus CaCl. 

 Plus MgClo 

 Plus SrCIj . 



Plus BaCl, plus NaCl . 

 Plus CaClo plus NaCl 

 PlusMgCla plus NaCl. 

 Plus SrCl, plus NaCl. . 



Plus CdCl2 . 

 Plus C0CI2 . 

 Plus MnCl2 

 Plus NiCl2 . 

 Plus ZnCL . 



LENGTH OF LIFE IN MINUTES 



Paramecium 



005 

 0005 



0.01 

 0.001 



o 

 3 



4 



10 



5 



4 



5 



13 



5 



8 



2 

 2 

 3 

 5 

 5 



0.05 

 0.005 



10 

 4 



7 

 20 



7 

 7 



10 

 25 



7 

 14 



5 

 4 



7 



0.1 

 0.01 



Euplotes 



0.0 



005 

 0.0005 



0.01 

 0.001 



12 

 20 



20 

 4 



10 



15 



5 



15 



18 



25 



5 



28 



2 



2 



3 



30 



30 



0.05 

 0.005 



20 



7 



12 



23 



5 



15 



40 



60 



5 



45 



3 

 3 

 3 



0.1 

 0.01 



25 

 10 



17 



33 



4 



20 



35 



60 



4 



40 



5 

 3 



and by Crozier^^ to penetrate living tissue most readily, and by 

 Loeb to be the most efficient in inducing artificial parthenogenesis. 

 In many physiological processes it is almost impossible to reverse 

 or protect against the action of cyclic compounds (Hober).-^ If 

 the cyclic acid is mixed with NH4CI there is little decrease in 

 toxicity, for the salt itself is deadly. With KCl there is a fair 

 amount of antagonism, and with NaCl still more; the antagonistic 

 power of both increases with the concentration, even for Euplotes. 



